The use of both (meth)acrylate compositions and epoxy resins in adhesive, sealing and coating technology is widespread. (Meth)acrylate compositions are notable for a high early strength and rapid curing, and epoxy resins are notable for a high final strength.
In order to utilize advantages of both technologies, hybrid systems comprising (meth)acrylates and epoxides are produced. Such hybrid systems are described, for example, in EP 1 431 365 A1 and EP 0 160 621 A1. With these compositions, an elevated temperature in the range from about 120 to 150° C. is needed for the curing of the epoxy resin, and they are thus unsuitable for thermally sensitive substrates.
There is a further reason not to use heat-curing compositions, for example, in applications including those where the composition is applied over a large area, and where the substrate provided with the composition, owing to its dimensions, cannot directly be heated homogeneously and simultaneously over the entire area, for example in an oven, such that the composition could cure. This is the case, for example, with large-area coatings, such as in the case of floor coverings. Uneven heating and the associated uneven curing of heat-curing compositions can lead in such a case to stresses within the cured composition.
Known heat-curing compositions are likewise unsuitable for the adhesive bonding of substrates with different coefficients of thermal expansion, since they have different contractions as they are cooled after the curing of the adhesive, which can result in unfavorable stresses in the adhesive bond.
The hardeners known to date for epoxy resins, such as aliphatic amines, which enable curing of the epoxy resin even at room temperature are unsuitable for use in a hybrid system comprising (meth)acrylates and epoxides, because they inhibit the free-radical polymerization reaction of the (meth)acrylate monomers and hence an optimal early strength is not achieved.